Metabolism Fueling Cell Growth

Chapter 6: Metabolism: Fueling Cell Growth Chapter Notes  Don’t worry too much about the details of Glycolysis, Cellular Respiration, or Photosynthesis onward  These topics are covered on pp 144-151 and pp 156-163  Note, however, that we will cover Glycolysis and Cellular Respiration in class at least from the perspectives of the importance of NAD+ regeneration Important Point: Products of Microbial Metabolism Important Consequences of Microbial Metabolism  Beer, wine, and other alcoholic beverages  Bread (all of above are mostly products of the yeast Saccharomyces cerevisiae)  Products of lactic-acid bacteria (LAB) including sour milks, various cheeses, half-sour pickles, sauerkraut, etc (e.g., of Lactococcus spp & Lactobacillus spp.)  Organic solvents including acetone (product of Clostridium acetobutylicum), butanol (ditto), and, of course, ethanol (product of S cerevisiae)  Acetic acid (vinegar)  Biochemical identification of bacterial species  Unique (e.g., not found in animals) targets for antimicrobial action  Disease (e.g., dental caries) Metabolism = Catabolism + Anabolism sum = metabolism Pay particular attention to those words in bold in this figure Bioenergetics (see Fig 6.3) More generally, sun or reduced inorganic chemicals (ocean vents) More generally, photoautotrophs (or just autotrophs) E.g., glucose More generally, chemoheterotrophs Note that bacteria don’t have mitochondria: aerobic bacteria “are” mitochondria! Metabolism Terms & Concepts  Metabolic pathway = highly evolved intracellular sequence of chemical reactions  Each step of a metabolic pathway usually is enzymatically catalyzed (and enzymes are proteins)  Substrates are molecules that enter into enzymatically catalyzed reactions  Products are what substrates are enzymatically converted into  Enzymes typically are very precise in terms of what substrates they will accept (often no more than one specific chemical) and they will convert a substrate into (often no more than one specific chemical)  Precursor molecules are found at the start of metabolic pathways  Intermediate molecules are found within metabolic pathways  End products are the molecules ultimately produced by a given metabolic pathway Chemical Energetics How cells “burn” glucose Enzyme Terms & Concepts  Enzyme names generally are indicated by an “ase” ending, e.g., dehydrogenase (lysozyme is exception)  Enzymes have active sites (a.k.a., catalytic sites)  Cofactors are non-protein components of enzymes; they can be organic or inorganic  Coenzymes are organic cofactors; they generally are carriers of other molecules or ions  NAD+ for example is a coenzyme An Enzyme and Coenzyme Mediated Catabolic Pathway Glycolysis (see Fig 6.14) Glucose NAD+ NADH ATP ATP Pyruvate An Enzyme and Coenzyme Mediated Catabolic Pathway Glycolysis (see Fig 6.14) An Enzyme and Coenzyme Mediated Catabolic Pathway Glycolysis (see Fig 6.14) Glucose     NAD+ NADH ATP ATP Pyruvate Regeneration of NAD + Regeneration of NAD + E.g., see Fig 6.17-6.19 (6.16-6.18) Glycolysis Pyruvate (2e-) Regeneration of NAD +  Glycolysis   Pyruvate (2e-)     above is why aerobes need O2 (see Fig 6.20) Lactic Acid Fermentation Glycolysis (see Fig 6.20) Ethanol Fermentation Bread Glycolysis Beer Simple Fermentation Pathways Mixed-Acid Fermentation This is why we Fart!  Other Fermentation Pathways Other Fermentation Pathways Beer, wine, bread Swiss cheese Flatulence! LAB & our own muscles Anaerobic Respiration …employs an inorganic molecule other than O2 as a terminal electron acceptor Hydrolytic Enzymes  Amylases = enzmes that hydrolyze starches to their constituent glucoser subunits  Disaccharidases = enzymes that hydrolyze dissacharides to constituent monosaccharides  β-galactisidase is the most famous of disaccharidases; it breaks down the sugar lactose (into galactose and glucose)  Lipases = enzymes that hydrolyze fats (into glycerol or and fatty acids)  Proteases = enzymes that break down proteins  Deaminases = enzymes that remove amino groups from individual amino acids  The resulting products can be used as alternatives to glucose as carbon and energy sources  Chemolithotrophs (a.k.a., chemoautotrophs) utilize substances other than organic compounds as energy sources and get their organic carbon from CO2 Link to Next Presentation [...]... cyclic catabolic pathway ATP – Energy Currency of Cells ATP, ADP, and Metabolism Oxidation-Reduction (Redox) Oxidation-Reduction (Redox) Oxidation-Reduction (Redox) Note NAD+ (not “NAD”) Note that 2 hydrogen ions are removed along with the 2 electrons (only one H+ ends up attached to NAD+, hence the charge change) Overview of Metabolism An Enzyme and Coenzyme Mediated Catabolic Pathway Glycolysis